ORIGINAL ARTICLE
Renal Cell Carcinomas With Papillary Architecture
and Clear Cell Components
The Utility of Immunohistochemical and Cytogenetical Analyses
in Differential Diagnosis
Stefano Gobbo, MD,*w John N. Eble, MD,* Gregory T. MacLennan, MD,z
David J. Grignon, MD,* Rajal B. Shah, MD,y Shaobo Zhang, MD,* Guido Martignoni, MD,w
Matteo Brunelli, MD,w and Liang Cheng, MD*
Abstract: Although histologic features enable an accurate
diagnosis in most renal carcinomas, overlapping morphologic
findings between some renal neoplasms make subclassification
difficult. Some renal carcinomas show papillary architecture but
are composed extensively of cells with clear cytoplasm, and it is
unclear whether they should be classified as clear cell renal cell
carcinomas or papillary renal cell carcinomas. We analyzed the
immunohistochemical profiles and the cytogenetic patterns of 14
renal carcinomas showing papillary architecture in which there
were variable amounts of cells with clear cytoplasm. The
patients were 8 women and 6 men (mean age: 54 y). Immunohistochemistry and fluorescence in situ hybridization analysis
distinguished 2 different groups. The first consisted of 10 renal
cell carcinomas with strong immunoreactivity for a-methyl
coenzyme A racemase, of which 9 also expressed cytokeratin 7.
All of these neoplasms showed gains of chromosome 7 or 17 and
chromosome Y was lost in all the male patients whereas 3p
deletion was detected only in one case. In the other 4 renal cell
carcinomas, cytokeratin 7 was not detected and a-methylacylCoA racemase was positive in only 1. In these neoplasms, no
gain of chromosome 7 or 17 and no loss of chromosome Y were
observed, whereas 3p deletion was detected in 3 of them. None
of the 14 neoplasms showed immunoreactivity for TFE3. The
combined use of immunohistochemistry and cytogenetics
enabled us to provide a definitive diagnosis for 12 of 14 renal
cell carcinomas with papillary architecture and clear cell components: 9 cases were confirmed to be papillary renal cell
carcinomas and 3 cases were confirmed to be clear cell renal cell
From the *Departments of Pathology and Laboratory Medicine,
Indiana University School of Medicine, Indianapolis, IN;
zDepartments of Pathology and Laboratory Medicine, Case Western
Reserve University, Cleveland, OH; yDepartments of Pathology and
Laboratory Medicine, University of Michigan, Ann Arbor, MI; and
wDipartimento di Patologia, Universitá di Verona, Verona, Italy.
Supported by Fondazione Cassa di Risparmio di Verona; Diagnostica
Molecolare in Oncologia; Ministero Istruzione, Università e Ricerca
(MiUR).
Correspondence: Liang Cheng, MD, Department of Pathology and
Laboratory Medicine, Indiana University School of Medicine, 350
West 11th Street, Clarian Pathology Laboratory Room 4010,
Indianapolis, IN 46202 (e-mail: liang_cheng@yahoo.com).
Copyright r 2008 by Lippincott Williams & Wilkins
1780
carcinomas. Despite these ancillary techniques, 2 cases remained
unclassified. Our study establishes the utility of these procedures
in accurately classifying the great majority of renal cell carcinomas with these findings.
Key Words: kidney, neoplasia, classification, papillary clear cell
renal cell carcinoma, molecular classification, immunohistochemistry, cytogenetic, fluorescence in situ hybridization,
unclassified renal cell carcinoma
(Am J Surg Pathol 2008;32:1780–1786)
C
lear cell renal cell carcinoma and papillary renal cell
carcinoma are the most common carcinomas of the
renal tubular epithelium and distinguishing them from
one another is important because they have different
prognoses, and it is sometimes important in assigning
patients to evolving adjuvant therapy protocols.1,8,14,25
Although most of the time they can be distinguished
easily in routine sections, occasionally, overlapping
morphologic findings make classification difficult. According to the World Health Organization (WHO)
classification of neoplasms of the kidney, clear cell renal
cell carcinoma typically is composed of solid, alveolar,
and acinar growth patterns of cells with clear cytoplasm
surrounded by a distinct cell membrane. Typically, they
contain a regular network of small thin-walled blood
vessels. Papillary renal cell carcinomas are typically
composed of papillae covered by small cells with scanty
cytoplasm (type 1) or by cells with eosinophilic cytoplasm
(type 2). Rarely, renal cell carcinomas are encountered in
which there are areas of papillary architecture, but there
are extensive populations of cells with clear cytoplasm.
In this situation, it is unclear whether they should be
classified as clear cell renal cell carcinomas or papillary
renal cell carcinomas. As papillary and clear cell renal
cell carcinomas show different immunophenotypes and
different characteristic cytogenetic abnormalities,24 we
evaluated the immunophenotypes of 14 renal neoplasms
with papillary architecture and extensive components
of neoplastic cells with clear cytoplasm, and additionally
Am J Surg Pathol
Volume 32, Number 12, December 2008
Am J Surg Pathol
Volume 32, Number 12, December 2008
Renal Cell Carcinomas With Papillary and Clear Changes
evaluated the cytogenetic characteristics of these neoplasms using fluorescence in situ hybridization (FISH).
obtained by incubating sections in 3% H2O2 for 15
minutes. Localization of bound antibodies was performed
with a peroxidase-labeled streptavidin-biotin system
(DAKO, LSAB2 Kit) with 3,3-diaminobenzidine as a
chromogen. Appropriate positive controls for each antibody were run concurrently and showed adequate
immunostaining.
MATERIALS AND METHODS
Cases
Fourteen renal neoplasms with areas of papillary
architecture and variable proportions of cells with clear
cytoplasm were identified in the surgical pathology
archives of the participating institutions. The original
pathologists varied in their interpretation of the findings:
3 were considered to be clear cell renal cell carcinomas, 2
were considered to be papillary renal cell carcinomas, and
9 were considered to be renal cell carcinoma, unclassified
(Table 1).
Clinical findings were obtained from medical
records. Sections cut at 4-mm thickness were stained with
hematoxylin and eosin and the cases were reviewed. These
neoplasms were staged according to the TNM system,18
and graded according to Fuhrman et al.15 For immunohistochemistry and FISH, we selected paraffin-embedded
tissue blocks containing neoplastic tissue with papillary
architecture and clear cell morphology as well as adjacent
non-neoplastic renal parenchyma.
Immunohistochemical Staining
Immunohistochemistry was performed with the
following antibodies: cytokeratin 7 (CK7) (DAKO,
Carpintera, CA; clone OV-TL 12/30; prediluted);
a-methylacyl-CoA racemase (AMACR) (DAKO; clone
P504S; 1:100 dilution); and transcription factor E3
(TFE3) (Santa Cruz Biotechnology, Santa Cruz, CA;
1:1600 dilution). Briefly, slides were deparaffinized twice
in xylene for 5 minutes and rehydrated through graded
ethanol solutions to distilled water. Antigen retrieval was
performed by heating sections in citrate buffer
(AMACR), ethylenediaminetetraacetic acid buffer
(TFE3), or enzymatically with proteinase K (CK7).
Inactivation of endogenous peroxidase activity was
FISH
Series of 4-mm slides were prepared from buffered
formalin-fixed, paraffin-embedded tissue blocks. The
slides were deparaffinized with two washes of xylene, 15
minutes each, and subsequently washed twice with
absolute ethanol, 10 minutes each, and then air-dried in
the hood. Next, the slides were treated with 0.1 mM citric
acid (pH 6.0) (Zymed, CA) at 951C for 10 minutes, rinsed
in distilled water for 3 minutes followed by a wash of
2 standard saline citrate (SSC) for 5 minutes. Digestion
of the tissue was performed by applying 0.4 mL of pepsin
(5 mg/mL in 0.1 N HCl/0.9 NaCl) (Sigma, St Louis, MO)
at 371C for 40 minutes. The slides were rinsed with
distilled water for 3 minutes, washed with 2 SSC for
5 minutes, and air-dried. FISH was performed with
centromeric a-satellite DNA probes for chromosomes 7
(CEP 7, Spectrum Green), 17 (CEP 17, Spectrum
Orange), Y (CEP Y, Spectrum Green), 3 (CEP 3,
Spectrum Orange), and subtelomeric probe for 3p25
(3pTel25, Spectrum Green). All of the probes were from
Vysis (Downers Grove, IL) and were diluted with
tDenHyb1 (CEP 7-CEP 17 and CEP Y) and tDenHyb 2
(CEP 3-3pTel25) (Insitus, Albuquerque, NM) in a ratio of
1:100, respectively. Diluted probe (5 mL) was applied to
each slide in reduced light conditions. The slides were
then covered with a 22 22-mm cover slip and sealed
with rubber cement. Denaturation was achieved by
incubating the slides at 831C for 12 minutes in a
humidified box and hybridization at 371C overnight.
The cover slips were removed and the slides were washed
twice with 0.1 SSC/1.5 M urea at 451C (20 min for
TABLE 1. Clinical Findings and Diagnosis Before and After Revision and Molecular Analyses
Case No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Age
Sex
ESRD
Follow-up
Original Diagnosis
49
55
79
77
77
31
59
41
58
54
41
48
29
56
F
M
F
M
M
F
F
F
F
M
M
M
F
F
No
No
No
No
Yes
No
No
Yes
No
No
No
No
No
No
NED (74 mo)
NA
NED (19 mo)
LNM (13 mo)
NED (15 mo)
NED (14 mo)
NED (25 mo)
NED (25 mo)
NA
NED (57 mo)
LNM (50 mo)
NA
NA
NA
Papillary RCC
Unclassified RCC
Unclassified RCC
Unclassified RCC
Unclassified RCC
Unclassified RCC
Clear cell RCC
Clear cell RCC
Papillary RCC
Unclassified RCC
Unclassified RCC
Clear cell RCC
Unclassified RCC
Unclassified RCC
Diagnosis After Revision
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
Unclassified
RCC
RCC
RCC
RCC
RCC
RCC
RCC
RCC
RCC
RCC
RCC
RCC
RCC
RCC
Diagnosis After
Immunohistochemical and
Cytogenetical Analyses
Unclassified RCC
Papillary RCC
Papillary RCC
Papillary RCC
Papillary RCC
Papillary RCC
Papillary RCC
Papillary RCC
Papillary RCC
Papillary RCC
Unclassified RCC
Clear cell RCC
Clear cell RCC
Clear cell RCC
ESRD indicates end-stage renal disease; F, female; LNM, lymph node metastasis; M, male; NA, not available; NED, no evidence of disease; RCC, renal cell carcinoma.
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Gobbo et al
Am J Surg Pathol
each), followed by a wash with 2 SSC for 20 minutes,
and with 2 SSC/0.1% NP-40 for 10 minutes at 451C.
The slides were further washed with room temperature
2 SSC for 5 minutes. The slides were air-dried and
counterstained with 10 mL 4,6-diamidino-2-phenylindole
(Insitus, Albuquerque, NM), covered with cover slips,
and sealed with nail polish.6,7,10 The slides were examined
using a Zeiss Axioplan 2 microscope (ZEISS, Gottingen,
Germany) with the following filters from Chroma
(Chroma, Brattleboro, VT): SP-100 4,6-diamidino-2phenylindole, FITC MF-101 for Spectrum Green (CEP
7, Y, and 3pTel25), and Gold 31003 for Spectrum Orange
(CEP 3 and 17). The images were acquired with a CCD
camera and analyzed with MetaSystem Isis Software
(MetaSystem, Belmont, MA). Five sequential focus
stacks with 4 mm intervals were acquired and then
integrated into a single image to reduce thickness-related
artifacts.
We performed FISH analysis with the same probes
(CEP 7, 17, 3, and 3pTel25) in classic clear cell renal cell
carcinoma and classic papillary renal cell carcinoma
as controls.
Pathologic Findings
In Situ Hybridization Analysis
The method of analysis was partially described,
previously.3–5,11,17,21 In brief, for each slide, 100 to 150
nuclei from neoplastic cells were scored for signals from
probes under the fluorescence microscope with 1000
magnification. Non-neoplastic kidney parenchyma was
used as control. Definitions of chromosomal gains and
losses of chromosomes 7, 17, and Y were based on the
Gaussian model and related to the non-neoplastic
controls. Any tumor with a signal score beyond the
cutoff value was considered to have had a gain or loss of
the specific chromosome. The cutoff values for each probe
were set at the mean ± 3 SDs of the control values.
Statistical method to analyze 3p deletion was based upon
previous studies of deletion of chromosomes 1p and 19q
in oligodendrogliomas.13,27
RESULTS
Clinical Findings
The patients were 8 women and 6 men (mean age:
54 y) (Table 1). Two patients suffered from end-stage
renal disease owing to autosomal dominant polycystic
kidney disease (case 5) and autoimmune nephritis (case
11). Six patients underwent a radical nephrectomy and
8 were managed by partial nephrectomy. Follow-up data
were available for 9 patients. The patient in case 4 had
retroperitoneal lymph node metastasis confirmed by
needle biopsy 13 months after the nephrectomy. The
patient in case 11 had metastases to retroperitoneal and
retrocaval lymph nodes and recurrence of disease in the
renal fossa 50 months after the partial nephrectomy. The
other patients were alive without recurrence or metastasis
after a mean follow-up period of 33 months (Table 1).
1782
Volume 32, Number 12, December 2008
Grossly, the neoplasms were well circumscribed and
localized to the renal cortex; cut surfaces were tan-yellow
or brown with varying degrees of hemorrhage and
friability. Necrosis was grossly evident in 4 cases.
Histologically, all neoplasms showed areas composed of papillary structures covered by medium-sized
cells (Fig. 1). In some cases, the papillary structures were
densely packed, resulting in a solid appearance, whereas
in some others the solid areas showed a tubulo-alveolar
architecture. Neoplastic cells with clear cytoplasm made
up 20% to 90% of the total neoplastic area
(mean = 54%). Focally, papillae were entirely covered
by clear cells. The tumor cells showed variable degrees of
cytoplasmic clarity; often, the cytoplasm had a microvesicular or finely granular appearance similar to the
cytoplasm of foamy macrophages that were frequently
present within papillary cores and in spaces between the
papillae. Usually, the nuclei were positioned centrally or
basally, and nuclear grade was quite homogeneous
throughout the neoplasms. Necrosis was present in 7
renal cell carcinomas, and was frequently associated with
cholesterol clefts. Psammoma bodies were present in 2
neoplasms. Needle biopsies of the metastatic cancer in
case 4 showed a papillary tumor composed of small cells
without cytoplasmic clearing. After review of the sections
stained with hematoxylin and eosin, using the diagnostic
criteria of the WHO classification, all 14 neoplasms
were considered to be unclassified renal cell carcinomas
(Table 1).
Immunohistochemistry and FISH
The results of the immunohistochemical procedures are summarized in Table 2. Eleven neoplasms
showed strong immunoreactivity for AMACR. Nine
neoplasms showed diffusely positive immunostaining
for CK7, and none showed immunoreactivity for
TFE3. The papillary and clear cell areas showed similar
degrees of immunostaining for AMACR and CK7,
although the staining tended to be somewhat more
membranous than cytoplasmic in areas of clear cell
change (Figs. 1C, D).
The results of the FISH analyses are summarized in
Table 3. Using the established criteria for chromosome
gains and losses and for 3p deletion (see Methods), 9
neoplasms showed gains of chromosome 7; 9 showed
gains of chromosome 17 and 4 neoplasms from 6 male
patients showed loss of chromosome Y. Chromosome 3p
deletion was detected in 4 cases. FISH analysis from areas
of papillary renal cell carcinoma and from areas with
clear cell morphology in the same tumor showed similar
results.
The combined morphologic, immunohistochemical,
and cytogenetic approaches allowed us to classify 12 of 14
previously unclassified renal cell carcinomas as papillary
renal cell carcinomas (9 cases) or clear cell renal cell
carcinomas (3 cases) (Table 1).
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2008 Lippincott Williams & Wilkins
Am J Surg Pathol
Volume 32, Number 12, December 2008
Renal Cell Carcinomas With Papillary and Clear Changes
FIGURE 1. Renal cell carcinomas with papillary architecture and clear cell component. A (case 4), Microscopic field showing papillae of typical
papillary renal cell carcinomas at top left and a solid area composed of clear cells at lower right. B (case 4), Higher power magnification of the solid area
composed of clear cells shown in (A). The papillae are densely packed creating a ‘‘solid’’ appearance that resembles clear cell renal cell carcinoma.
C (same field as image A), Neoplastic cells in both the typical papillary area and the area of clear cells show strong immunostaining for a-methylacyl-CoA
racemase (AMACR). D (same field as image A), Tumor cells in both the typical papillary area and the area of clear cells show strong diffuse
immunostaining for cytokeratin 7 (CK7). E, An area of clear cells in case 2, showing clear cells admixed with abundant foamy macrophages, which are
often present in the papillary cores. F, High power view of an area of clear cells in case 2, showing cells with grade 3 nuclei and cytoplasm that is partially
clear and partially granular; a few macrophages are also present at upper right. G, Fluorescence in situ hybridization with centromeric probes for
chromosomes 7 (Spectrum Green) and 17 (Spectrum Orange) showing nuclei with 3 hybridization signals for both probes (case 3). H, Fluorescence
in situ hybridization with a centromeric probe for chromosome Y (Spectrum Green) showing a nucleus of a lymphocyte from a male patient with 1
hybridization signal and adjacent neoplastic cells entirely lack Y chromosomes. I, J (case 13), Renal cell carcinoma with clear cell components (I) and
pseudopapillary architecture (J). The pseudopapillary growth pattern occurs as a result of cell drop-off in which the tumor cells situated away from the
blood supply die, and those close to the vessels are preserved. K, Fluorescence in situ hybridization with centromeric probes for chromosomes 7 (Green)
and 17 (Orange) showed two hybridization signals for each probes in tumor nuclei (case 13). L, Fluorescence in situ hybridization with a centromeric
probe for chromosome 3 (Spectrum Orange) and subtelomeric probe for 3p25 (Spectrum Green) showing nuclei with deletion of 3p (case 14).
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2008 Lippincott Williams & Wilkins
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Gobbo et al
Am J Surg Pathol
Volume 32, Number 12, December 2008
TABLE 2. Pathological and Immunohistochemical Findings
Case No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Side
Size (cm)
Grade
Necrosis
Foamy Macrophages
Clear Area (%)
CK7
AMACR
TFE3
L
R
L
L
L
L
L
L
L
R
R
R
L
R
8.3
3.7
10
2.4
2.5
3
3
3
1.9
3
7.3
2.5
7.5
14
G3
G3
G4
G2
G2
G1
G2
G2
G3
G3
G3
G3
G3
G4
Yes
Yes
Yes
No
Yes
No
No
No
Focal
Focal
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
No
No
No
No
20
40
20
30
20
25
60
90
80
75
80
90
75
50
++
++
++
++
++
++
++
Neg
85%
++
Neg
Neg
Neg
Neg
++
++
++
++
++
++
++
++
++
++
++
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
AMACR indicates a-methylacyl-CoA racemase; CK7, cytokeratin 7; L, left; Neg, negative; R, right.
DISCUSSION
We studied the cytogenetic changes and the immunophenotypes of 14 renal cell carcinomas containing
areas of papillary architecture and with substantial
components of neoplastic cells with clear cytoplasm.
After review of sections stained with hematoxylin and
eosin, all were considered to be renal cell carcinoma,
unclassified. Immunohistochemical and cytogenetic
studies distinguished 2 different groups among these.
The larger group was composed of 10 neoplasms, all of
which were positive for AMACR immunostaining
and 90% of which were positive for CK7. They further
showed gains of chromosomes 7 or 17, and all of the
neoplasms from male patients showed loss of chromosome Y. No deletion of 3p was found in 90% of these
neoplasms. The second group consisted of 4 neoplasms
(cases 11 to 14 in the tables). In these renal cell
carcinomas, the immunohistochemical reactions for
CK7 were negative and the reaction for AMACR was
positive in only 1. No gains of chromosomes 7 and 17
were detected in any of the renal cell carcinomas and in
the 2 neoplasms from men; there was no loss of the
Y chromosome. However, 3p deletion was detected in 3 of
the neoplasms. The neoplastic cells with clear cytoplasm
had the same cytogenetic findings as did neoplastic cells
without clear cytoplasm. The combined use of immunohistochemistry and cytogenetics enabled us to provide a
definitive diagnosis for 12 of 14 renal cell carcinomas with
papillary architecture and clear cell components: 9 cases
were confirmed to be of papillary renal cell carcinomas
and 3 cases were confirmed to be of clear cell renal cell
carcinomas. Despite these ancillary techniques, 2 cases
remained unclassified. Our study establishes the utility of
these procedures in accurately classifying the great
majority of renal cell carcinomas with these findings.
In the cases we finally considered as papillary renal
cell carcinomas, the similarities between the cytoplasmic
appearance of the neoplastic epithelial clear cells and the
cytoplasm of foamy macrophages suggest a possible
common endocytotic mechanism that results in cytoplasm
TABLE 3. Percentages of Nuclei With Different Numbers of Signals and Results for Chromosomes 7, 17, Y and 3p Deletion
Analysis
CEP 7
Case
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1784
CEP 17
1 Signal 2 Signals 3 Signals
(%)
(%)
(%)
6
38
8
8
16
4
2
6
6
8
20
37
22
26
30
59
28
32
40
50
14
40
32
44
70
63
77
71
65
4
64
60
44
46
84
54
62
48
10
0
1
3
Result
Gain
No gain
Gain
Gain
Gain
Gain
Gain
Gain
Gain
Gain
No gain
No gain
No gain
No gain
1 Signal 2 Signals 3 Signals
(%)
(%)
(%)
6
11
20
32
36
16
10
12
22
6
24
26
21
30
47
42
44
40
52
44
48
60
74
42
68
74
77
69
47
47
36
28
12
40
42
28
4
52
8
0
2
1
CEP Y
Result
Gain
Gain
Gain
Gain
Gain
Gain
Gain
Gain
No gain
Gain
No gain
No gain
No gain
No gain
0 Signals 1 Signal
(%)
(%)
—
96
—
98
100
—
—
—
—
100
20
19
—
—
—
4
—
2
0
—
—
—
—
0
80
81
—
—
r
3p25
Result
CEP
3/3p
Result
—
Loss
—
Loss
Loss
—
—
—
—
Loss
No loss
No loss
—
—
1.74
1.13
1.10
1.09
1.05
1.08
1.08
1.22
1.02
1.05
1.32
1.52
2.13
1.79
Deleted
Not deleted
Not deleted
Not deleted
Not deleted
Not deleted
Not deleted
Not deleted
Not deleted
Not deleted
Not deleted
Deleted
Deleted
Deleted
2008 Lippincott Williams & Wilkins
Am J Surg Pathol
Volume 32, Number 12, December 2008
Renal Cell Carcinomas With Papillary and Clear Changes
clarification. In fact, areas of tumor cell cytoplasmic clearing
were often associated with more global degenerative
changes that result in necrosis and hemorrhage, events that
may incite absorptive behavior in surviving tumor cells. In
case 3, the metastatic tumor showed typical features of
papillary renal cell carcinoma without any of the cytoplasmic clearing that has been observed in the primary tumor.
This observation suggests that the cytoplasmic clearing may
not be due to a genetic characteristic of these renal cell
carcinomas, but instead might be induced by the local
metabolic environment. Most of these neoplasms showed
aggregates of foamy macrophages in the stroma of the
papillary cores and areas of cholesterol cleft formation,
findings often seen in classic type 1 papillary renal cell
carcinoma. The neoplasms we finally considered as clear cell
renal cell carcinomas (cases 12 to 14 in the tables) were
actually high-grade renal cell carcinomas. The areas with
papillary architecture were associated with a discohesive
pattern suggesting that the appearance of papillae was the
result of degeneration rather than a growth pattern of the
neoplasms. This architectural pattern seems to occur as a
result of cell drop-off in which the tumor cells situated away
from the blood supply die and those close to the vessels are
preserved.
Considering that clear cell renal cell carcinomas can
show areas of pseudopapillary architecture, and papillary
renal cell carcinomas may exhibit components of cells
with clear cytoplasm, reaching an accurate diagnosis may
be challenging, especially in core needle biopsies, which
are being employed preoperatively in an increasing
number of cases. Our results validate the utility of
immunohistochemistry and FISH analyses in the differential diagnosis of these renal cell carcinomas.
The immunohistochemical panel we used in this
study enables one to distinguish accurately between
papillary renal cell carcinoma, clear cell renal cell
carcinoma, Xp11.2 translocation renal cell carcinoma,
and the recently described clear cell papillary renal cell
carcinoma. Papillary renal cell carcinomas often show
positive immunostaining for AMACR and CK7,12,24,31
whereas clear cell renal cell carcinomas usually lack
immunoreactivity for AMACR and CK7.22,31 All the
renal neoplasms considered as papillary renal cell
carcinoma in the current study showed strong immunoreactivity for AMACR and 9 of 10 showed diffusely
positive immunostaining for CK7. All of the neoplasms
that turned out to be clear cell renal carcinoma were
negative for CK7 and only one showed a positive reaction
for AMACR. Nuclear labeling for TFE3 protein by
immunohistochemistry, a distinctive and diagnostic feature of Xp11.2 translocation renal cell carcinoma, was not
identified in any of the neoplasms.2
The cytogenetic findings in the renal cell carcinomas
in the current study were those typically seen in papillary
renal cell carcinoma in 10 cases and those typically seen in
clear cell renal cell carcinoma in the 3 other cases. Gains
of chromosomes 7, 17 and loss of the Y chromosome,
which were observed in the first group of our cases, are
commonly identified in papillary renal cell carcinoma and
these numerical aberrations occur early in the evolution
of papillary renal cell neoplasia.3,4,9,19,23 The second
group presented deletion of chromosome 3p, which is
not only considered one of the primary events in the
development of clear cell renal cell carcinoma, but has
also been documented in a small proportion of papillary
renal cell carcinomas as in our case 1.20,26,29,32
Recently, a distinctive tumor characterized by
papillary architecture and composed entirely of clear
cells has been described as arising in kidneys with or
without end-stage renal disease and is designated as
‘‘clear cell papillary renal cell carcinoma’’.17,30 Although
these neoplasms may be difficult to distinguish from
papillary renal cell carcinomas with clear cell changes on
the basis of morphologic findings alone, these two
entities have different immunohistochemical and cytogenetical profiles. AMACR immunoreactivity and gains
of chromosomes 7 and 17 are not observed in clear
cell papillary renal cell carcinoma, whereas papillary renal
cell carcinomas typically express AMACR and show
gains of chromosomes 7 and 17. On the other hand
clear cell papillary renal cell carcinomas show a strong
immunoexpression for CK7 and lack the deletion of 3p,
whereas clear cell renal cell carcinomas are negative for
CK7 and frequently show 3p deletion.
Another renal tumor that may be difficult to
distinguish from papillary renal cell carcinoma with clear
cell changes is Xp11.2 translocation renal cell carcinoma.
This neoplasm is typically composed of cells with abundant
clear to faintly eosinophilic cytoplasm, arranged in nests and
papillary structures. Psammoma bodies are often present, a
finding that is sometimes also observed in papillary renal
cell carcinoma.12 The tumor cells of Xp11.2 translocation
carcinomas characteristically show positive nuclear immunostaining for TFE3, a finding that was not observed in any
of the cases in our series.2
Other investigators have analyzed renal cell carcinomas with papillary architecture and significant components of clear cells.16,28 Fuzesi et al studied 3 such cases
with classic cytogenetic analysis, and demonstrated clonal
aberrations of chromosome 3, leading to loss of terminal
3p segments, in all of them. Salama et al included in their
study only renal cell carcinomas, with papillary architecture, showing more than 75% of cells with clear
cytoplasm. They analyzed 7 neoplasms with FISH using
centromeric probes for chromosomes 7 and 17 and with
loss of heterozygosity analysis, with markers mapping in
the short arm of chromosome 3. They found no trisomy
of chromosome 7 or 17 and in 6 cases there was loss
of heterozygosity of 3p. Consequently, the neoplasms
analyzed in these 2 studies were regarded as clear cell
renal cell carcinomas, on the basis of cytogenetic studies
alone. Neither of these investigations was done in concert
with immunostainings of these renal cell carcinomas. We
found the same cytogenetic findings in the second group
of our cases (cases 12 to 14) that were considered clear cell
renal cell carcinomas. Cases 1 and 11 in our study were
considered to be unclassified renal cell carcinomas.
Although case 1 showed trisomies of 7 and 17, it also
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showed 3p deletion. Case 11 showed neither the trisomy
of chromosomes 7 and 17 typical of papillary renal cell
carcinoma, nor the loss of chromosome 3p typical of clear
cell renal cell carcinoma. In addition, the labeling for
AMACR and absence of labeling for CK7 in case 11 is
not typical of either of the two entities in question. Cases
2 to 10 showed a cytogenetic pattern opposite to those in
previous studies and we considered them to be papillary
renal cell carcinomas. Our FISH results are in keeping
with the immunohistochemical characteristics of the renal
cell carcinomas that we studied.
In summary, we report a series of renal cell
carcinomas with papillaryarchitecture and areas of clear
cell morphology. Their immunohistochemical profiles
and cytogenetic patterns allowed us to distinguish between
papillary renal cell carcinomas and clear cell renal cell
carcinomas in the great majority of cases. We present a
suggested panel of immunohistochemical and cytogenetic
findings that are useful in establishing an accurate
diagnosis in these cases and in distinguishing them from
other renal neoplasms with similar histologic findings.
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